In August 2017, food safety authorities in the Member States of the European Union (EU) and the food industry have implemented significant monitoring of eggs for residues of fipronil, which is being conducted to ensure that the recall measures are protecting consumers. There is also interest in egg products, meat, and organs from laying poultry. In order to monitor fipronil abuse and ensure the safety of such foods, a simple, sensitive, reliable, and validated method for determining residues of fipronil in chicken egg is needed.

The default EU MRL for fipronil in eggs is set at 0.005 mg/kg with a residue definition of the sum of the parent fipronil and the metabolite fipronil sulfone, expressed as fipronil.2 Fipronil and fipronil sulfone can be determined by either LC-MS/MS or GC-MS(/MS) after a generic extraction such as QuEChERS , followed by clean up with SPE, either in dispersive (dSPE), or in pass-through modes. When analyzing these compounds using LC-MS/MS with electrospray in negative ion mode, consideration should be given to the impact of matrix effects from co-eluting co-extractives that can suppress the signal, reducing the sensitivity, accuracy, and robustness of the method. A balance must be struck between providing a rapid analytical method and the need for accurate quantification and robustness.

In this application note, we report the results of a validation of a modified QuEChERS method for the determination of fipronil and its metabolite fipronil sulfone, in eggs by liquid chromatography-tandem quadrupole mass spectrometry, which meets the SANTE criteria (SANTE/11945/2015).